8o i'KN TTi f:skoi.a. M.-X. Kl. 



Still :iM<)tli(i- slice shows the syinplectite in a parti}' uralitized state, 

 embeddeil in laij^e individuals oi" plagioclase and a hornblende-plagioclasc- 

 niass, and linalJN , the most perfect state of amphibolitization is represented by 

 a thin section, whit'h cr)ntains c)nly hoi-nblcndc-plagioclase-symplectite in which 

 the new development of the pi-ism shapes in the symplectic hornblende is notable. 



\n the previous discussion I have regarded the structural evidence as 

 sufhcient to decide whethei- an eclogite has undergone a posterior alteration 

 into the amphiholite faciès or has been brought under the conditions of the 

 lattei- l)eloi-<- perlect consolidation, and 1 believe the evidence to be con- 

 vincing for the lonnei- alternativ, when symplectites occur, and for the 

 latter, when brown hornblende lilling the interstices, or large and anhedral 

 individuals of plagioclase as a mesostasis, are present. But a granular 

 liornblende-|)lagioclase-niass might also be taken for metamorphic, and it 

 mav be difficult to know exactly the mode of origin. 



Professor V. M. (ioldschmidt privatelv suggested the following reasoning: 

 If an eclogite-mass has undergone a posterior change, this will have worked 

 inward from the border and we shall find the border-zones most altered, 

 while the o[)posite will be the case, if a change of facies has happened 

 during the crystallization^, as the inner parts of a magma mass must have 

 consolidated last and at lowest temperatures. 



From my field experience I know only the case of alteration of the 

 border-zones and have not studied in the field those occurrences whose 

 structures point to a change of facies. Concerning the Romsdalshorn eclogite- 

 hornblende-gabbro, Th. Kjerulf' states that its border-zones are amphibolitic. 

 The occurrence of alteration at the borders, of course, would not controvert 

 a change of facies in the midst the mass. 



The change of facies may occur before the final consolidation, but 

 there is another possibility, that the change of conditions might cause a 

 perfect or partial refusion of the eclogite. Under certain conditions this 

 must necessarily happen on the reduction of pressure, in consequence of the 

 large difference of volume between the eclogite and its magma. Refusion 

 is the more likely, the larger the mass ot eclogite. 



On the Age of the Gneiss Formation of Nordfjord and Møre. 



The problem concerning the geological age of the gneiss formation 

 under consideration does not belong to the subject of the present treatise. 

 Here we want only to state that its age is still unknown. 



Two different suppositions may possibly be considered: (ll That the 

 gneiss of Nordtjord and Møre is Archaean or 1 2) that it belongs to the 

 Caledonian eruptives. 



Whatever mav be the age of these rocks, the labradoiite-rocks, eclo- 

 gites and the olivine-rocks belong to the same age-complex as the gneiss. 



' Loc. cit. 



